Canal engineers build aqueducts to bridge canal boats over rivers and large stream such as Seneca Creek. Eleven aqueducts were needed between here and the canal's western terminus at Cumberland, Maryland; all required skilled quarrymen and stonemasons, and large outlays of scarce capital.
Seneca Aqueduct opened to traffic in 1833, and along with through-boats from the west, carried a substantial local traffic in lime, grain, fertilizer and sandstone to and from farms and industries around Seneca. Made of red sandstone from nearby bluffs, it has long been one of the most admired canal structures.
Freshets and flooding on Seneca Creek have always caused problems, and finally in September, 1971, almost 50 years after the canal closed, a violent local flood swept away one of the arches.
The last locktender at Seneca was Johnny Riley, whose former lock and lockhouse are at the east end of the aqueduct. "I don't care what hour of the night it was," recalled a former boatman, "any hour of the night you boat to his lock and holler . . . there was his lantern waving you ahead."